FIG. 10 is a partial sectional view of a known magnetic sensing element (spin valve type thin film element) cut along a direction parallel to a surface facing a recording medium.
In FIG. 10, reference numeral 1 denotes a substrate layer made of Ta. A seed layer 2 made of a metal, e.g., Cr, having a body-centered cubic structure (bcc structure) is disposed on the substrate layer 1.
A multilayer film T, in which an antiferromagnetic layer 3, a pinned magnetic layer 4, a non-magnetic material layer 5, a free magnetic layer 6, and a protective layer 7 are deposited sequentially, is disposed on the seed layer 2.
The protective layer 7 is formed from Ta, the non-magnetic material layer 5 is formed from Cu, the free magnetic layer 6 and the pinned magnetic layer 4 are formed from a Heusler alloy, e.g., Co2MnGe, and the antiferromagnetic layer 3 is formed from PtMn.
Electrode layers 10 and 10 are disposed on the top and the bottom of the multilayer film T, and a direct current serving as a sensing current flows in a direction perpendicular to the film surfaces of the multilayer film.
An exchange coupling magnetic field is generated at the interface between the antiferromagnetic layer 3 and the pinned magnetic layer 4, and the magnetization of the pinned magnetic layer 4 is pinned in the height direction (Y direction shown in the drawing).
Hard bias layers 8 made of a hard magnetic material, e.g., CoPt, are disposed on both sides of the free magnetic layer 6, and the top, bottom, and end portions of the hard bias layers 8 are insulated by insulating layers 9. The magnetization of the free magnetic layer 6 is aligned in a track-width direction (X direction shown in the drawing) by longitudinal bias magnetic fields from the hard bias layers 8.
When an external magnetic field is applied to the magnetic sensing element shown in FIG. 10, the magnetization direction of the free magnetic layer is varied relative to the magnetization direction of the pinned magnetic layer, and the resistance of the multilayer film is changed. In the case where a sensing current flows at a constant current value, this change in resistance is detected as a change in voltage, so that the external magnetic field may be detected.
The magnetic sensing element including the free magnetic layer made of a Heusler alloy is described in Japanese Unexamined Patent Application Publication No. 2003-218428.
It is described in Japanese Unexamined Patent Application Publication No. 2003-218428 that the free magnetic layer is made of a Heusler alloy, e.g., a CoMnGe alloy. A configuration in which a NiFe layer is deposited on the CoMnGe alloy is also described.
However, it has been found that a suitable free magnetic layer cannot be formed simply by depositing the NiFe layer on the layer made of a Heusler alloy.